Receptacles are designed to receive fluid from nozzles. Receptacles transfer the received fluid into a connected storage tank. One example of a receptacle is a car gasoline port. One example of a nozzle is a gasoline dispenser at a gas station. One example of a connected storage tank is a car gas tank. Some fluids, such as liquid natural gas (LNG), compressed natural gas (CNG), liquefied petroleum gas (LPG), among others, are transferred via specialized nozzles and receptacles.
LNG and LPG may be stored in liquid form at cryogenic temperatures (e.g., −150 degrees C. or −238 degrees F.). During the transferring process between nozzle and receptacle, a portion of LNG/LNG may heat up and vaporize into gas. This gas expands to occupy all accessible areas of the nozzle and receptacle. When the transferring process is complete, a portion of the vaporized gas will remain in the receptacle. When the nozzle is eventually disconnected from the receptacle, this remaining gas is often intentionally vented into ambient atmosphere.
CNG may be stored under high pressures. During the transferring process between nozzle and receptacle, CNG may expand and occupy all accessible areas of the nozzle and receptacle. When the transferring process is complete, a portion of the gas will remain in the receptacle. When the nozzle is eventually disconnected from the receptacle, this remaining gas is often intentionally vented into ambient atmosphere.
Even when the remaining gas is intentionally vented from the receptacle, new gas will flow from the storage tank into the receptacle, thus pressurizing the receptacle. The next time a nozzle is inserted into the receptacle, the remaining gas will oppose the insertion of the nozzle, thus making the coupling process physically difficult.